Health & Wellness

Is Your Fish Oil Rancid?

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By Dr. Anne-Marie Chalmers

Think about fish oil. If your gut reaction is “yuck,” you are in good company. Whether it’s from remembering Grandma’s cod liver oil or taking today’s capsules, many people believe fish oil ought to taste bad.

The truth is that omega-3 supplements shouldn’t taste like yesteryear’s salmon. And if your fish oil does, it may be rancid.

What Is Rancidity?

Fish and fish oil spoil — or ‘oxidize’ — more easily than other foods because they are rich sources of omega-3 fatty acids. Omega-3s are known for their anti-inflammatory properties and role in promoting brain health. But their chemical structure also makes them highly prone to oxidation.

If the omega-3s oxidize, their molecular structure changes and the molecules break down into byproducts. These byproducts, known as lipid peroxides, give off the unpleasant smell and taste of spoiled fish.

How quickly omega-3s oxidize depend on numerous factors: how the fish was caught, how the fish oil was processed, and how the final product was distributed, to start. Reducing exposure to oxygen, heat and light, as well as adding antioxidants, will help protect the oil. But if the oil has already started to oxidize, it is just a matter of time before it turns rancid.

How Rancidity Affects Your Health

Besides tasting and smelling bad, rancid fish oil could be harmful. Animal studies indicate that oxidized fatty acids may cause organ damage and inflammation. And two recent studies comparing unoxidized and oxidized oil found that oxidized fish oil had a negative effect on cholesterol levels and could be linked with Alzheimer’s disease. In comparison, unoxidized oil provided expected health benefits.

How to Combat Rancidity

Rancid fish oil is common. Studies from Canada, New Zealand, Norway and other nations have found that a high percentage of omega-3 supplements exceed acceptable oxidation limits.

Yet fresh fish oil exists and can provide consumers with a relatively inexpensive, safe way to improve health. To ensure you are getting a fresh product, do the following:

1. Evaluate your current product.

The best way to tell whether or not your omega-3 supplement is fresh is to put it through the taste and smell test. If you have capsules, break them open. If your nose gets a whiff of a strong fishy smell, get something else.

2. Make smart purchases.

Fish oil is a food substance that is highly perishable, just like milk or seafood. Beware of labels that have a two to three year expiration date. These products have likely been sitting on the shelf for years. You can also ask manufacturers to share their fish oil’s oxidation numbers, better known as the peroxide, anisidine, and TOTOX values. These values will give you a good picture of the oil’s freshness level.

3. Remember that bigger is not always better.

Look for small containers when buying fish oil. The longer a fish oil is stored, even in gelatin capsules, the greater the chance it will turn rancid.

4. Keep it cold.

Buy fish oil that you can store in the freezer or refrigerator. Low temperatures slow down the enzymatic time bomb that is ticking away.

5. Use it or lose it.

All fish oils will turn rancid with time. When you first buy fish oil, use it up the same way you would fresh fruits and vegetables.

Omega-3 Innovations is located at 727 Commerce Dr., Venice, FL 34292,

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